1. Field of the Invention.
This invention relates to the use of alkaline earth salts of polycarboxylic acid monoesters as a catalyst for the ethoxylation or propoxylation of compounds containing active hydrogen atoms.
2. Discussion of Related Art.
Various catalysts have been used for the aforementioned polyalkoxylation reaction; for example, calcium and strontium hydroxides, alkoxides and phenoxides (EP-A No. 00 92 256), calcium alkoxides (EP-A No. 00 91 146), barium hydroxide (EP-B No. 0 115 083), basic magnesium compounds, for example alkoxides (EP-A No. 00 82 569), magnesium and calcium fatty acid salts (EP-A No. 0 85 167).
The catalysts mentioned above are attended, inter alia, by the disadvantage that they are difficult to incorporate in the reaction system and/or are difficult to produce.
Other typical polyalkoxylation catalysts are potassium hydroxide and sodium methylate.
A narrow range of the degree of polyalkoxylation is of particular importance for fatty alcohol polyalkoxylates, cf. JAOCS, Vol. 63, 691-695 (1986), and HAPPI, 52 -54 (1986). Accordingly, the so-called "narrow-range" alkoxylates have above all the following advantages:
low pour points,
relatively high smoke points,
fewer mols alkoxide to achieve solubility in water,
fewer hydrotropes for introduction into liquid universal detergents,
relatively faint odor through the presence of free (unreacted) fatty alcohols, and
reduced pluming in the spray-drying of detergent slurries containing fatty alcohol polyalkoxylate surfactants.
The range or rather homolog distribution of fatty alcohol polyalkoxylates depends mainly on the type of catalyst used. A measure of the homolog distribution is the so-called Q value according to the following relation: EQU Q=n*p.sup.2
in which n* is the average number of adducts (average degree of ethoxylation) and p is the percentage of the adduct having a certain EO degree which is predominantly formed. Accordingly, a high Q value signifies a narrow homolog distribution range.